Distributed computer systems utilize the technique of distributing application execution. More specifically, an application server locally executes an application program and provides the application output data to clients/network users who then display the results on a display screen coupled to their local computer. By performing the application processing functions at the server and displaying the application output at the client, these distributed systems make the best use of server and client resources, i.e., the more capable server performs the compute and memory intensive application processing functions while the client, with potentially greater video performance, displays the output. During execution of the application program, a user of the client views the application output data on the client's display and interacts with the application program via keyboard or mouse inputs. The client user's inputs correspond to requests to the application server to perform certain actions that affect the operation of the application program. The application server passes these requests to the application for further processing. The application server also intercepts the application output data, generated by the application program and typically targeted to the operating system of the application server, and transmits all or part of the data to the client for display. From the perspective of the user, the application program seems to be executing locally even though it is actually being executed on a remote server and just being displayed locally.
The performance of distributed systems depends to a large degree on the capability of the network, which couples the client and the server, and therefore on the amount of graphical data (corresponding to the application output data) that is transmitted over the network. Since the application server and the client workstation are generally linked only by a transport mechanism (such as serial lines, telephone lines, local area networks and wide area networks) that possesses lower bandwidth than would be otherwise available if the application program were executing locally, the perceived performance of the distributed system may suffer. Accordingly, manufacturers of distributed systems/software continually strive to improve the performance of such systems.